Carboxymethylated cellulosic wound dressing

ABSTRACT

Wound dressings in the form of a body-shaped component are composed of body-shaped cellulosic fabric which has been carboxymethylated at the wound contacting surface. The body-shaped component composed of a fabric comprising a cellulosic material is subjected to a carboxymethylation process to carboxymethylate the cellulosic material at the wound-contacting surface.

FIELD OF THE INVENTION

This invention relates to wound dressings of the type in which thewound-contacting surface is composed of a cellulosic material that hasbeen subjected to carboxymethylation.

BACKGROUND ART

It is known to use carboxymethylated cellulosic materials in situationswhere a high degree of moisture absorbency is required. For example,WO93/12275 describes the production of various absorbent products suchas disposable nappies (diapers), tampons, sanitary napkins, incontinencepads and the like. The advantage of carboxymethylated cellulosicmaterials, for example the carboxymethylated solvent-spun cellulose(lyocell) material to which WO93/12275 is particularly directed, is thatthey are capable of absorbing many times their own weight of water oraqueous fluid. This causes the carboxymethylated fibres to form a gel,which effectively serves to entrap the absorbed moisture.

One application in which absorption of moisture is of importance is thedressing of wounds, particularly exuding wounds. Carboxymethylatedlyocell materials have been successfully utilised in wound dressingmaterials, and their use for this purpose is described, for example, inWO94/16746 and WO00/01425. The gel-forming characteristic of suchmaterials is of particular advantage in the treatment of wounds, sincethe gel tends to prevent adherence and therefore minimises the wounddamage and pain which can often occur when a wound dressing is removed.The attention of the reader is directed to the full disclosures of thesedocuments for a fuller discussion of the preferred degree ofcarboxymethylation to achieve optimal results, and of the reactionconditions by means of which carboxymethylation may advantageously beachieved in practice.

The techniques described in these documents have resulted incommercially successful wound dressings, which are essentially flat butflexible, for example rectangular, circular or of some other planarshape and which comprise a wound-contacting portion composed ofcarboxymethylated lyocell fibre or fabric, often used in conjunctionwith an adhesive backing layer to provide adhesion to an area of skinadjacent to or surrounding the wound. Such dressings have proved to bevery effective in the treatment of localised wounds and are particularlysuperior to conventional dressings composed of fibrous gauzes andwaddings for use with moist or exuding wounds. However, their usefulnessis limited in respect of large-scale wounds (such as extensive burns)and in fragile areas (such as may be associated with cancerous orfungating wounds), where the use of adhesive attachment means isdifficult. Dressing retention can also be a problem in awkwardly shapedparts of the body such as armpits.

It is also known to provide wound dressings composed of certainmaterials in the form of a garment or an inflexible three-dimensionalshape complementary to the shape of a body part. For example, GB2,357,286 discloses a process for preparing a shaped polyurethanearticle for use as or in a wound dressing, for example a glove dressingfor a whole hand, in which a last having the desired three-dimensionalshape is provided, an aqueous layer is applied over the last, a layer ofan isocyanate-capped prepolymer is applied over the last to react withthe aqueous layer and form a polyurethane foam layer, which is thenstripped from the last. Also, U.S. Pat. No. 5,437,621 discloses amedical dressing for covering a wound, for example in the shape of aglove, comprising material having at least three layers, namely aninnermost layer comprising a porous polyethylene film which enablesmoisture to be wicked away from the injury, a middle layer comprising anabsorbent material for absorbing the moisture from the innermost layer,and an outer layer comprising a flexible, waterproof and breathablematerial. Other body-shaped wound dressings are disclosed in EP0,769,283 and WO86/04811.

To the best of our knowledge, however, it has not previously beensuggested to provide body-shaped wound dressings incorporating acarboxymethylated cellulosic fabric. This may well be because it can bedifficult to create a body-shaped wound dressing from carboxymethylatedcellulosic fibre because of the inherent weakness of such fibre, whichmay preclude normal knitting into body-shaped format such as gloves, andbecause of the need to keep the fibre dry during processing to stop itabsorbing moisture and becoming sticky.

The present invention therefore seeks to provide improved wounddressings in the form of body-shaped components having awound-contacting surface and methods of manufacturing them.

DISCLOSURE OF THE INVENTION

We have found that improved wound dressings in the form of a body-shapedcomponent, such as a garment or part of a garment, having awound-contacting surface are composed of carboxymethylated cellulosefabric, especially fabric which has been carboxymethylated at least atthe wound-contacting surface after provision in body-shaped form. Suchdressings are particularly suitable for use on moist or exuding woundsthat are either extensive or otherwise difficult to treat withconventional dressings. The body-shaped dressings have athree-dimensional shape as opposed to being flat, albeit they areflexible or deformable. Their shape is such that when placed on a bodypart they are able to remain there of their own accord and do not falloff without the aid of an adhesive layer, although it is not necessaryfor them to have a tight fit with the body part for which they aredesigned.

The invention provides a method of manufacturing a wound dressing in theform of a body-shaped component, characterised in that the wounddressing is composed of carboxymethylated cellulosic fabric and has beenobtained by a method comprising the steps of forming a body-shapedcomponent comprising a cellulosic material and subjecting saidbody-shaped component to a carboxymethylation process tocarboxymethylate the cellulosic material at the surface which in use ofthe dressing contacts a wound.

Cellulosic fabrics which have not been carboxymethylated are strongerthan the corresponding carboxymethylated cellulosic fabrics. Thus, theymay be formed into body-shaped components by a wide variety of methodsin any manner convenient.

A number of advantages stem from the provision of a carboxymethylatedcellulose wound dressing in the form of a garment or other body-shapedcomponent. Most importantly, the dressing may literally be tailor-madeto suit the particular size and shape of the wounded body part to betreated. For example, a dressing for an extensively wounded hand or awounded finger may be provided in the form of a glove or a finger stall;a dressing for an infant suffering widespread burns may be provided inthe form of a baby's body suit; and a dressing for wounds to the uppertorso may be provided in the form of a vest or T-shirt. Numerous furtherexamples of suitably shaped dressings for specific purposes (e.g. tubes,socks, balaclavas, whole head or face masks, underpants, etc) willimmediately suggest themselves to those skilled in the art. Thedressings can therefore posess the flexibility and other desirableadvantages of cellulosic textile material.

The inherent gel-forming characteristic of carboxymethylated cellulosicmaterials may be turned to particular advantage in dressings accordingto the invention, since gel formation on the surface of the body-shapedcomponent which is destined to come into contact with the skin of thepatient in the vicinity of the wound will greatly ease the manner inwhich the body-shaped component may be slid over the wounded area of thebody and mininmise the pain associated with this operation. Thus, forexample, the internal surface of a dressing according to the invention(for example a glove) may be sprayed with water or saline solutionbefore being applied to the patient.

Because of the inherent weakness and moisture sensitivity ofcarboxymethylated cellulose it can be very difficult to construct abody-shaped component from already carboxymethylated fabric or fromfabric produced from already carboxymethylated fibres. According to themethod of the invention the wound dressings are manufactured bysubjecting finished garments or other body-shaped components ofcellulosic material which is not carboxymethylated to acarboxymethylation process after formation of the garment or otherbody-shaped component. Indeed, a further significant advantage of theinvention is that there is a ready supply of garments or otherbody-shaped components suitable for conversion into dressings accordingto the invention, since virtually any body-shaped component made ofcellulosic fabric (for example cotton, or a manmade cellulosic substancesuch as lyocell) may be used. Such materials can essentially bepurchased “off the shelf”.

The body-shaped component need not be composed exclusively of cellulosicmaterial but may be made of a mixture of different cellulosic fibresand/or of mixtures of cellulosic with non-cellulosic fibres, providedthat an appropriate degree of carboxymethylation is achieved. If amixture of cellulosic and non-cellulosic fibres is to be subjected tocarboxymethylation any non-cellulosic fibres should be able to withstandthe carboxymethylation conditions. The body-shaped component optionallyincludes a yarn with elastic properties such as Lycra or other spandexyarn. This will assist it to assume the shape of the wearer onceapplied.

The body-shaped component can incorporate one or more medicaments. Forexample, an antimicrobial agent, or an antibiotic, or an anaesthetic, oran anti-inflammatory agent, or a skin protective agent, or a substanceintended to negate malodours, can be incorporated. Suitableantimicrobial agents include silver or silver-containing compounds,povidone iodine and formulations which release hydrogen peroxide.

The incorporation of a medicament can be achieved in a variety of ways.For example, silver or other metal ions can be chemically bound byion-exchange reactions. Other medicaments might be added during the laststage of, or in an additional stage following, the carboxymethylationprocess by contacting a solution of the medicament with the body-shapedcomponent which is then dried, leaving a deposit of the medicament onthe surface of the body-shaped component.

In some preferred embodiments, the body-shaped component is one piece offabric, for example manufactured by a continuous knitting process.Alternatively, the body-shaped component may be constructed from two ormore pieces of fabric sewn or otherwise fastened together, in which casecare should be taken to ensure that the pieces are fastened together bymeans, such as a suitable sewing yarn (for example nylon yarn), that isnot degraded by the carboxymethylation process.

Where the garment is tubular or encompassing, it can be provided with azone of weakness or a removable connector such as a pull-thread actinglike a rip-cord, so that the garment can be opened up and peeled off forremoval. It could also be formed with suitable connectors, such as hookand loop connectors, for example Velcro (™), to assist removal of thewound dressing.

Carboxymethylation may be achieved, for example, by sequential orsimultaneous treatment of the cellulosic material with a strong alkali,such as aqueous sodium hydroxide, and monochloroacetic acid or a saltthereof. The appropriate reaction conditions will depend upon thecomposition of the fabric and the degree of carboxymethylation requiredand will be readily apparent to the person skilled in the art; they may,for example, be identical or similar to those described in WO93/12275,WO94/16746 or WO00/01425, the contents of which are incorporated byreference herein and to which the reader is directed for further detail.

Desirably, the carboxymethylation is carried out in the presence ofindustrial methylated spirits (IMS), and IMS is preferably also used ina subsequent washing step, suitably along with water, as a cleaner andsteriliser. Such a method of subjecting the finished body-shapedcomponent to the carboxymethylation process has the added advantage ofproducing a sterile or near-sterile product as a result of cleaning withthe IMS/water mixture. It may therefore be unnecessary to provide afurther sterilisation step as would be unavoidable if an attempt were tobe made to produce the body-shaped component from cellulosic materialwhich had already been carboxymethylated. Contaminants such as grease,dirt and germs picked up during formation are removed and/or sterilisedduring the IMS cleaning step. The resulting carboxymethylatedbody-shaped component can then be packaged and further sterilised in asealed package by various methods such as gamma irradiation.

The degree of carboxymethylation is desirably such that, upon absorptionof moisture, the fibres at the skin-contacting surface of thebody-shaped component form a gel but preferably the fabric retainssufficient fibrous character that the body-shaped component retains itsintegrity during application to, use on and removal from the patient.The cellulosic material may be carboxymethylated only at thewound-contacting surface, or cellulosic material remoter from thatsurface may also be carboxymethlated, for example the cellulosicmaterial may be carboxymethylated throughout.

The invention is hereinafter described in further detail, by way ofexample only, with reference to the following Example carried out usinga commercially available body suit composed of 100% cotton and weighing62 g for a baby.

EXAMPLE

23.7 g of NaOH was added to 64.0 g of water and stirred with a glass rodto obtain a homogeneous solution. In a separate beaker, 35.6 g of sodiummonochloroacetate (SMCA) was added to 79.9 g of water and stirred toobtain a homogeneous solution. The solutions were then mixed and 162.1 gof industrial methylated spirit (IMS) added. The reactants were stirredquickly and the body suit was immersed in the mixture. The reactionvessel was then sealed and placed in a water bath at 73° C. for 95minutes. During the reaction, the flask was opened every 10 minutes toagitate the liquors physically and to turn over the body suit to ensureeven contact with the liquors.

After the treatment, the reaction mixture was neutralised with 43 mlglacial acetic acid for 10 min at 73° C. Two wash stages were thencarried out, each at 70° C. for 10 min. Wash liquors were made up of189.3 g IMS, 145 g water and 2.0 g citric acid. Tween 20 (a softeningagent) was then applied as the finish at 73° C. using 301 g IMS, 34.2 gwater and 2.0 g Tween 20 (polysorbate 20). During the wash andneutralisation stages, agitation was carried out using a glass rod.Finally, excess liquors were squeezed out by hand and the body suitdried in an oven at 50° C. for 2 hours.

When tested, the body suit was subjected to a subjective “gel feel”test. A satisfactory degree of slipperiness was detected, indicatingsuccessful carboxymethylation.

1-14. (canceled)
 15. A method of manufacturing a wound dressing in theform of a body-shaped component, wherein the wound dressing is composedof carboxymethylated cellulosic fabric and has been obtained by a methodcomprising the steps of forming a body-shaped component comprising acellulosic material and subjecting said body-shaped component to acarboxymethylation process to carboxymethylate the cellulosic materialat the surface which in use of the dressing contacts a wound.
 16. Themethod according to claim 1, wherein the fabric comprising a cellulosicmaterial is a woven, non-woven or knitted fabric composed of fibres of anatural cellulosic substance or of a man-made cellulosic substance or ofa mixture of such substances.
 17. The method according to claim 2,wherein the fabric comprising a cellulosic material is composed ofcotton or of lyocell or a mixture thereof.
 18. The method according toclaim 1, wherein the carboxymethylation process comprises the steps oftreating the fabric, either sequentially or simultaneously, with sodiumhydroxide and monochloroacetic acid or a salt thereof in the presence ofindustrial methylated spirits and subjecting the resulting material to awashing step with industrial methylated spirits.
 19. The methodaccording to claim 1, wherein the body-shaped component is in the formof a garment or part thereof.
 20. The method according to claim 1,therein the cellulosic material includes fibres and thecarboxymethylation process is carried out to provide a degree ofsubstitution such that, upon absorption of moisture, the fibres at thesurface of the body-shaped component form a gel but the fabric retainssufficient fibrous character so that the body-shaped component retainsits integrity during application to, use on and removal from the wound.21. The method according to claim 1, wherein the carboxymethylationprocess is carried out to carboxymethylate the cellulosic material notonly at the surface which in use of the dressing contacts a wound butalso to carboxymethylate the cellulosic material remote from thatsurface.
 22. The method according to claim 1, wherein the body-shapedcomponent is composed of a single piece of fabric.
 23. The methodaccording to claim 1, wherein the body-shaped component is composed ofat least two pieces of fabric sewn together with a yarn composed of amaterial that is not degraded by the carboxymethylation process.
 24. Themethod according to claim 1, wherein the fabric comprising a cellulosicmaterial also contains non-cellulosic fibre.
 25. The method according toclaim 10, wherein the fabric includes a non-cellulosic yarn with elasticproperties.
 26. The method according to claim 1, wherein it includes thestep of providing the dressing with a removable connector.
 27. Themethod according to claim 12, wherein the removable connector is a pullthread.
 28. A wound dressing in the form of a body-shaped componenthaving a wound-contacting surface, wherein it is composed of body-shapedcellulosic fabric which has been carboxymethylated at least at thewound-contacting surface.